Rex Raptor and Weevil Underwood appeared several times in Season 1. They're an obvious parody of Beavis and Butt-head (partially noting the fact that the usual Beavis and Butt-head intro is shown at the beginning of episode 4). Weevil is Beavis (the more hyperactive one who transformed into Cornholio in episode 4) and Rex is Butt-head (the calmer and marginally more intelligent of the two); the opposite of their real personalities. However, unlike Steve Lumis and Steve Umbra, the parody characters' voices surprisingly suits their actual appearance as Butt-head's personality fits well with Rex's resemblance of a stoner teenager and Beavis's voice works well to Weevil's appearance of a stereotypical nerd who is bug obsessive. He also tends to mislead/insult Weevil a lot as seen in their comment special and when watching Silent Hill. Both tend to laugh stupidly at regular intervals and try to make sexual innuendos out of everything they or someone else say (i.e. "You said 'region'!"). All in all, they're both incredibly idiotic, which, considering how unintelligent they are in the dub, only adds to the parody's humor. Weevil also repeats the word "fire!" in various episodes, a reference to Beavis' pyromania and the fact that all uses of the word "fire" were eventually banned on Beavis and Butt-head; however, Weevil says "fire" in a more flatter voice than Beavis. It's later revealed that Weevil somehow saved Kaiba from The Salesman. Rex apparently has a very short memory span, as he claims not to remember that Joey won his Red-Eyes from him (though he may have just been playing dumb as Joey brought it up as a counter when Rex was taunting him about not having his Red-Eyes). In the Other Abridged Movie, after losing to Kaiba he goes and dyes his hair.
At the start of season 4, Rex challenged Weevil to a race where they would outrun their own farts. Weevil accepted and both ran down the city block until the bumped into Gurimo. They proceeded to mock him for his Jedi-like appearance, until he challenged them to a Duel and took their souls. Their souls were later claimed by Rafael, who held on to them until Gurimo was defeated by Yami Yugi. Later in the season, Rex and Weevil sought out the power of the Seal of Orichalcos, the effect of which "retconned" their voices, temporarily making their voices resemble their English dub counterparts from the canon series.
According to Marik's Evil Council of Doom, Weevil enjoys Furbies and according to Yugi Gives An Apology, Raptor is one of the characters people want to see (which irritates Bakura who was thinking he might get more screen time).